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www.sgh.com

What’s New In ASCE 7-16?

Ronald O. Hamburger SE, SECBSenior Principal

Simpson Gumpertz & Heger Inc.

Presented to:TMS

San Diego, CANov. 4 2017

The Big Changes

• Title Change

• Chapter 1 – Performance Goals

– Service & Function

– Reliability Targets

– Updated Hazard Maps

• New Chapter on Tsunami Loads

• New Appendix on Fire Effects

• Complete Revision of Seismic Response History

Analysis Procedures

• New Seismic Site Class Coefficients

• New Cladding Wind Pressure Coefficients

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Title Change (also 2 Volumes)

Minimum Design Loads and Associated Criteria for

Buildings and Other Structures

• Hazard levels

• Intended Performance Goals

• Seismic detailing

• Protection against wind borne

debris

Chapter 1Performance

Goals

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1.3.3 Functionality

• Risk category IV structures and systems designed to

provide reasonable probability of functionality given any

of the design level hazards (ice, flood, rain, seismic,

snow, tsunami, wind)

• Affects:

– Outdoor generators

– Radio communications towers

– Roof-mounted HVAC (if necessary for function)

Table 1.3-1– Target Reliability other than Seismic, Tsunami or Extraordinary Events

Reliability Goals – Load other than Seismic

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Reliability Goals & Performance

Table 1.3-2– Target Reliability for Structural Instability Caused by Earthquake

Table 1.3-3– Target Reliability for Noncritical Member Failures Caused by Earthquake

Reliability Goals Seismic

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Updated Hazard Maps

Impact on ASCE 7-16

• New hazard maps for:

– Atmospheric Icing

• ¼” to ½” increase in susceptible areas

• Moderate increase in geographic coverage

– Seismic

• +/- 10% changes many places

• +/- 20% a few places

– Wind

• 10 – 15 mph reduction across non-hurricane prone regions

– Snow

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Wind Maps

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• ASCE 7-10 • ASCE 7-16

Snow Maps

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Snow Maps

Chapter 6Tsunami

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Scope

• Risk Category III & IV Structures within the Tsunami

Design Zone

• Other structures designated by building official

• Tsunamic Design Zone

– Based on 2,475 year tsunami run-up hazard

– Digital maps for: Alaska, California, Hawaii, Oregon, Washington

Tsunami Design Zone

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Tsunami Design Procedure

• Based on Tsunami Amplitude, shoreline distance,

ground elevation and friction, determine:

– Flood elevation

– Flood velocity

Design Evaluations

• Design for:

– Hydrodynamic forces

– Buoyancy

– Waterborne debris impact

• Load Case 1

– Maximum inundation depth + buoyancy

• Load Case 2

– 2/3 Maximum inundation depth

– Maximum velocity

• Load Case 3

– Maximum inundation depth

– 1/3 maximum velocity

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Evaluation Approach

• Linear static or nonlinear static procedure

• ASCE 41 Acceptance Criteria

– Risk Category II or III buildings – Collapse Prevention

– Risk Category IV buildings – Immediate Occupancy

Chapter 12Seismic

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Classical Design Response Spectrum

T

Sa(T)

TL10.2

SDS

SD1

SD1/T

SD1TL/(T)2

��� � 23� ���

�� � 23� ���

Where hazard is controlled by large-magnitude earthquakes, and site soils

are soft, the standard spectral shape is not appropriate

• Site specific site response analysis required where:

– Site Class E and SS > 1.0

– Site Class D or E S1 > 0.2g

Response Spectrum Rules

T

Sa(T)

TL10.2

SDS

SD1

SD1/T

SD1TL/(T)2

T

Sa(T)

TL10.2

SDS

SD1

SD1/T

SD1TL/(T)2

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Response Spectrum Rules

• Exceptions

– Site Class E,

• Site Class “C” Fa is used

– Site Class D,

• � ����

� �⁄� for values of T< 1.5Ts

• Cs factored by 1.5 for T>1.5TS

• Scaling of Response Spectrum Results

– Forces scaled to 100% of ELF Base Shear

Response History Analysis

• Linear procedure moved to Chapter 12

• Completely rewritten nonlinear procedure (Chapter 16)

– Must perform linear analysis first

– Ground Motions

• Uniform Hazard or Conditional Mean Spectrum

• 11 motions minimum

• Global Evaluation

– Unacceptable Runs

– Transient Drift

– Residual Drift

• Component Evaluations

– Reliability-based with load and resistance factors

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Chapters 26-30Wind

ASCE 7-10 v ASCE 7-16

• Except in hurricane areas, wind speeds have reduced by

about 10%

– More weather stations available now

– Increased forestation & urbanization

– Reliabilities of old maps “not right”

• At high altitude locations wind pressures can be reduced

considering the reduced density altitude

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High Altitude Wind Reduction

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Reno, Tahoe, Denver, Santa Fe

Flat Roof Pressures

2010 2016

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Appendix EFire Effects

Appendix

Fire Effects

• All structures comply with applicable fire protection

requirements of building code, or

• Performance-based approach

– Design fire scenarios

• Structural stability

• Egress

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On-lineHazard Tool

On-line Hazard Tool

• Replaces USGS and ATC Seismic and Wind Hazard

applets

• Input:

– Lattitude

– Longitude

– Site Class

• Output:

– Seismic: SS SMS, SDS, S1, SM1, SD1 + response spectra

– Ground Snow Load

– Basic Wind Speed

– Atmospheric Icing Thickness

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Summary

• Significant changes in wind and seismic design

• Enhanced recognition of performance-based procedures

• First ever adoption of Tsunami criteria

• Web-based Hazard Lookup

• Is now available for purchase

• Is referenced in IBC 2018

Thank you!